1. Field of the Invention
The present invention relates to a ferro-electric memory device having a hydrogen barrier film and a method of manufacturing the same.
2. Description of the Related Art
In recent years, ferro-electric memory devices (FeRAM: Ferro-electric Random Access Memory) using a ferro-electric capacitor have received a great deal of attention as a kind of nonvolatile semiconductor memory.
FIG. 50 is a sectional view of a conventional ferro-electric memory device. As shown in FIG. 50, in the conventional ferro-electric memory device, a MOSFET 15 having a gate electrode 13 and source/drain diffusion layers 14a and 14b is formed on a semiconductor substrate 11. An interlayer dielectric film 16 is formed on the MOSFET 15. A ferro-electric capacitor 22 is formed on the interlayer dielectric film 16. The ferro-electric capacitor 22 includes a lower electrode 18, ferro-electric film 19, and upper electrode 20. The upper electrode 20 is connected to a plate line (PL) 30 through a contact 28. The lower electrode 18 is connected to one source/drain diffusion layer 14a of the MOSFET 15 through a contact 17a. A bit line (BL) 34 is connected to the other source/drain diffusion layer 14b of the MOSFET 15 through contacts 29 and 33. In this ferro-electric memory device, the ferro-electric capacitor 22 is covered with a hydrogen barrier film 23 to prevent invasion of hydrogen into the ferro-electric capacitor 22.
However, the hydrogen barrier film 23 may deform by recrystallization in annealing after the ferro-electric capacitor 22 is processed or, deform by migration of the fence substance at a portion where a fence used in processing the ferro-electric capacitor 22 remains. Accordingly, the hydrogen barrier film 23 may have breaks. In this case, hydrogen invades from the contact 29 or the like near the ferro-electric capacitor 22 into it. The hydrogen invaded from breaks in the hydrogen barrier film 23 may degrade the capacitor characteristic.
A prior-art reference associated with the present invention is as follows.
[Patent reference 1] Jpn. Pat. Appln. KOKAI Publication No. 2002-353414.